As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - ON FLIGHT 2226, AIRCRAFT RETURNED TO FIELD. SHORTLY BEFORE LEVELING OFF AT FL210 CAUTION LIGHTS RUD PRESSURE AND RUD FULL PRESSURE ILLUMINATED. ON APPROACH BOTH CAUTION LIGHTS EXTINGUISHED. MAINTENANCE REMOVED AND REPLACED RUDDER DUAL PRESSURE REGULATOR. OPERATIONAL CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.